1. Field of the Invention
This invention relates to a control for a vehicle provided with a continuously variable speed system power transmission capable of continuously varying speed ratio.
2. Description of Prior Art
This applicant disclosed in Japanese prior patent applications No. 40747/82 and No. 67362/82 continuously variable speed system power transmissions for a vehicle which utilizes a continuously variable transmission (hereinafter defined "CVT") to run an engine with the minimum rate of fuel comsumption within the whole range of required horse power. In these transmissions of prior applications, to ensure responsive property in acceleration, a line of the optimum rate of fuel comsumption (a line connecting points which achieve the required horse power with the minimum rate of fuel consumption) is defined, as shown in FIG. 1, by being lowered from WOT (wide open throttle valve of intake system) downward by a predetermined torque allowance to carry out the normal running of an engine along this line of the optimum rate of fuel comsumption. Originally the engine is run the most preferably by WOT. In FIG. 2, the engine is specified such that air-fuel mixture is made lean relative to the stoichiometrical air-fuel ratio while the line of the optimum rate of fuel consumption coincides with the WOT line. However, if the engine running is specified as shown in FIG. 2, the whole engine output torque is reduced so that the maximum output horse power of the engine needed at the minimum can not be ensured and accelerating property depends disadvantageously only upon the responsive property of CVT.